Issue with Drum mode
  • I’ve recently completed my Anushri. The analogue signal path, the synth and the clk/kbd pages, the arpeggiator and the sequencer appear all to work fine, except for the drum page.

    Here, the sequencer does not run if the sequence is empty, and thus I have get the sequencer rocking through the kbd page. With syth sounds playing, turning any of the first 4 of the two multi-function knows appear to flick through crazy syth presets, either on some ultra high pitch resonant sound or something glitchy and low. No drum sounds – just the synth, as I’m still able to affect the audio being sequenced in the drum page with the analogue signal path – filter, sub osc, pwm, fm etc.

    It’s probably soldering skills – I’ve had an issue with the 10 multi-functoin knobs not working at all due to soldering issue on one of the connector pins between control and main boards.

    My question is, where are the brains of the drum mode, so that I can hone-in on the area of possible soldering mishaps.

    Having asked that, I’m guessing it’s the arduino, and I’ve really spent a lot of time going over the soldering, to save you guys having to ask for high res pictures! It seems though that there is either a short somewhere, if there is a dedicated bit of hardware relevant to the drums alone, or software issue, so I need to re-program the avr.

    I’ve tried booting while holding run/stop.

    Am I missing something in my reasoning? Suggestion much appreciated.
    Peter

  • ... I failed to say that I get the sequencer going by playing some notes on a midi keyboard, or by holding hold in the clk/kbd page, and then back in the drum mode, turning the knobs does crazy stuff to the sequenced audio coming from the synth. No drum sounds. All knovs doe equally crazy audio glitches, as if flicking through some preset matrix.

    excuse the ramblings.

  • I might be misunderstanding the question, but here goes, maybe something here will help: – the sequencer indeed does nothing, unless midi notes {e.g. a keyboard) are inputted OR the key combo in the manual is pressed. – After checking for shorts, I clean the unpowered board with a toothbrush – there’s a good thread on cleaning the board accessible through the search function here. – The Anushri is analogue and mine takes awhile to ‘warm up.’ It can do some strange things in the meantime. – If I were troubleshooting, I’d save reflashing the Atmega for last, if you bought that chip from Mutable. – The drum sound can be isolated by using the 1/8 drum output on the top. Do you get any drum sound, when in drum mode, using only the 1/8 drum out? I assume you’re connecting the Anushri to an amp or powered speakers.

  • > The Anushri is analogue and mine takes awhile to ‘warm up.’ It can do some strange things in the meantime.

    This is misleading. The only thing that needs “warm up” is the circuit setting up the pitch of the VCO, and the only impact is a slight detuning of the VCO. The synth is operational as soon as it boots. If it does strange things, then there’s something wrong with your build.

    > My question is, where are the brains of the drum mode, so that I can hone-in on the area of possible soldering mishaps.

    This is the ATMega328p chip (there’s no arduino here). If there’s something wrong with it, the synth does not boot at all, no sound. If the synth boots, there’s no problem with it…

    I suspect that the 10 multi-functions are not working correctly. Try resoldering all the 4051s and the connector between the two boards.

    Check C2, R5, C4 – anything wrong with these parts and the drums signal won’t go anywhere.

    Audio samples appreciated!

  • Thank you very much for the replies.

    Indeed I was thinking about the ATMega328 when I was talking about the arduino. You’re probably right about the 10 multi-functions. I’m seeing strange behavior with the glide control, as having it down to minimum gives heaps of glide, which is set to zero when the control is at around 9 o’clock. Resistor value issue?

    I’ll look into the soldering of the 4051s and the suggested caps and resistors. If that fails, audio samples will follow!

  • it might be the capacitors around the quartz as well, if you say that it takes some time to “warm up”. Verify their values, and verify the soldering around the quartz.

  • @pichenettes – Thanks for the information and correction. I’ll recheck.

    @MicMicMan – Thank you, I’ll start there.

    What a great support community!

  • Hello again helpful people,

    I’ve re-soldered the 4051s, checked C2, R5, C4, the caps around the crystal, a host of other stuff and still – the 10 multi-function knobs work for the synth and clk/kbd pages, but not for the drum page. I’m attaching audio of the symptoms. Here I have re-set the Anushri by booting and holding run/stop. I change the glide and then sequence tempo to prove it the knobs work on synth and clk/kbd pages and then I move on to the drum page where moving any of the 10 multi-functions produces the same effect of crazy audio glitches. I then move the filter to show that it was indeed the synth being affected by drum mode controls.

    I have tried to isolate the drum sounds by using the CV jacks and I get the crazy synth audio through that as well… which seems like a severe issue.

    AnushriDrumModeIssue.mp3
    431K
  • Reading the 3rd run errata seems like I went ahead an soldered the male header on the control board. Could this be the reason for my troubles? ;)

  • Absolutely not.

  • Is the VCO DAC output stable when this glitch happens?

  • I’m going through the tests with an oscilloscope and noticed that, and this might be unrelated –

    E: VCO reset pulse. 0V, with a short pulse close to +5V at each period of the VCO.

    For me, it’s sitting at -4.7, with the pulses appearing at around 0.3V.. is this ok?

  • I doubt this is possible… To which point is the ground of your scope attached?

  • @pichenettes – by “ is the VCO DAC output” do you mean this test:
    11: DAC clock signal. Bursts of two sequences of 8 steps at 10 MHz.

    If so – it’s stable during the glitching.

    Having now done all the tests I note:

    No signal in points S and T corresponding to the drum signal
    The test at point 16, the Drums PWM signal – I think this could be a lead. I have small bursts of three occurring every 15 micro seconds.. 66MHz.. they’re in the order of 0.1V in magnitude.. maybe my power supply is noisy.

    When recommending a power supply you mention that it should have little ripple. Is this as in, less ripple is better, or some ripple preferable?

    Thank you for all the help!

  • Check the voltage at the point labelled “VCO” on the board. This drives the VCO, it should stay at the same value unless you change the note you play.

    > maybe my power supply is noisy.

    If you have a scope, measure it!

    > When recommending a power supply you mention that it should have little ripple. Is this as in, less ripple is better, or some ripple preferable?

    As soon as it does stay above 7.5V all the time, it’s fine.

  • > Check the voltage at the point labelled “VCO” on the board. This drives the VCO, it should stay at the same value unless you change the note you play.

    The VCO voltage changes during the glitching. Turning any of the 4 leftmost knobs in either rows (when in drum mode) causes the VCO voltage to jump between two values. Hence the glitching appears to be the VCO jumping between two values.. there’s a short somewhere.. Could it be that a capacitor got fried during soldering and is acting as a short?

  • @pichenettes
    >I doubt this is possible… To which point is the ground of your scope attached?

    I missed this question..
    The ground is connected to the pads for extra headers labelled -12V GND +12V, next to the voltage regulators.

    I’ve double checked this. I’m testing all the pins marked red at +5V, green pins at -5V, and yet the test at the pin marked E, the voltage drops to -5V and the pulse is around 9V, so it’s just under +5V.. perhaps I’m onto something here..